Problem: Solve for $a$ : $-10 + a = -6$
Answer: Add $10$ to both sides: $ \begin{eqnarray} \\ -10 + a &=& -6 \\ \\ {+10} && {+10} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-10 + a} &\hphantom{=}& \hphantom{-6} \\ a &=& -6 {+ 10} \\ \end{eqnarray} $ Simplify. $ a = 4$